The production of high-energy high-voltage pulses is a fundamental requirement for many modern electronic applications. Prior art circuits for achieving pulses of this type include:                1. Cockcroft-Walton voltage multiplier        2. Marx Generators        3. Pulse ModulatorsAll of the foregoing prior art circuits have problems over which improvement would be desirable.        
The Cockcroft-Walton voltage multiplier is the simplest type of voltage multiplier. First built in 1932 by Cockcroft and Walton for nuclear physics experiments. It is formed from a voltage multiplier ladder network of capacitors and diodes to generate high voltages. Unlike transformers, a Cockcroft-Walton voltage multiplier does not use an iron core transformer. Using only an oscillator, capacitors and diodes, these voltage multipliers can step up relatively low voltages to extremely high values, while at the same time being far lighter and cheaper than transformers. In such voltage multipliers, the voltage across each stage of the cascade is equal to only twice the peak input voltage, whereby it has the advantage of using relatively low cost components.
The Cockcroft-Walton voltage multiplier has a number of drawbacks, however. As the number of stages is increased, the voltages of the higher stages begin to ‘sag’, primarily due to the AC impedance of the capacitors in the lower stages. When supplying an output current, the voltage ripple rapidly increases as the number of stages is increased. For these reasons, Cockcroft-Walton voltage multipliers with large number of stages are typically used only where relatively low output current Is required. It would therefore be desirable to provide a circuit for achieving a high voltage pulse that avoids such drawbacks.
The Marx Generator is a more advanced type of voltage-multiplication circuit that relies on charging a plurality of capacitors in parallel and then discharging them in series. The parallel-series switching operation is usually accomplished using spark gaps as switches. It is extensively used for simulating the effects of lightning during high voltage and aviation-equipment testing. The spark gaps are placed as close as possible together for maximum ultraviolet (UV) light exchange between them (emitted by the arcs) for minimum jitter.
Among the drawbacks of the well-known Marx generator is that it suffers from reliability problems due to wear in the spark gap switches, causing irregular operation and increase in the amount of jitter. These problems are a serious disadvantage. It would be desirable to provide a circuit for achieving a high voltage pulse that avoids the foregoing reliability and jitter problems.
A third prior art circuit for generating high voltage pulses is known as a pulse modulator. It was originally developed during the Second World War as power supplies for radar systems. The pulse modulator incorporate a Pulse Forming Network (PFN), which accumulates electrical energy over a comparatively long time, and then releases the stored energy in the form of a nominally-square pulse of comparatively short duration, for various pulsed power applications. In practice, a PFN is charged by means of a high voltage power source, then rapidly discharged into a load via a high voltage switch, such as a spark gap or hydrogen thyratron. While PFN's usually consist of a series of high voltage energy storage capacitors and inductors, they can also consist of just one or more capacitors. These components are interconnected as a “ladder network” that behaves similarly to a length of transmission line. Upon command, a high voltage switch then transfers the energy stored within the PFN into the load. When the switch “fires” (closes), the network of capacitors and inductors within the PFN creates a nominally square output pulse of short duration and high power. This high power pulse becomes a brief source of high voltage to the load. In most pulse modulator circuits, a specially-designed pulse transformer is connected between the PFN and load to improve the impedance match between the PFN and the load, so as to improve power transfer efficiency. A pulse transformer such as this is typically required when driving higher-impedance devices such as klystrons or magnetrons from a PFN. Because a PFN is charged over a relatively long time and then discharged over a very short time, the output pulse may have a peak power of megawatts.
Pulse modulators are limited by the requirement for a pulse transformer, which is slow, bulky and subject to saturation. It would be desirable to provide a circuit for achieving a high voltage pulse that avoids such drawbacks.
It is also known in the prior art that Class A amplifiers can be cascaded for use with continuous wave (e.g., sinusoidal) RF signals. However, such prior art cascaded amplifiers have the drawbacks of being bulky and inefficient. It would be desirable to provide cascaded Class A amplifiers that are smaller and more efficient.
Activation of electron tubes is the process by which the cathode is converted from its as-manufactured state into a functioning electron emitter. Typically, this process involves drawing current from the cathode through the anode, while the tube is still connected to a vacuum pumping system. Specific implementation varies with the type of cathode used. Activation requires supplying operating voltages equal to or greater than those normally encountered in operation of the tube. Activation takes place while the tube is still connected to an external vacuum pump system. This is done to facilitate the removal of impurities released from the cathode by the activation process. In the case of very high voltage tubes, the cost of suitable power supplies is very high. It would, therefore, be desirable to minimize the cost of high voltage power supplies and to simplify and expedite the manufacturing process.